The sustainability of resource utilization

There is a need for a method with which the sustainability of technological processes can be described quantitatively, and earlier work by De Wulf et al.(1) in cooperation with our laboratory has yielded a useful method based on thermodynamic principles. New insights however have led to a revision of this earlier work, and considerable improvements have been introduced. Most progress is made in quantitatively describing the sustainability of resource utilization. Instead of classifying resources either as renewable or as non-renewable, the new method is based on the depletion rates of resources, which account for many grades of resource renewability and which include also the size of natural reserves of resources. Also, this paper reviews the quantification of other aspects of process sustainability, explains the vital role of exergy, and discusses how the overall sustainability of a process should be determined.